The present invention relates to flat panel displays. More particularly, the present invention relates to systems for backlighting flat panel displays.
The principle of operation of flat panel displays is well known in the art. However, for purposes of understanding the present invention, it can be stated that flat panel displays, such as liquid crystal displays (LCDs), operate by modulating the transmissibility of light through a matrix of pixel elements when an electric field is applied. Since the effect is localized to selected pixel elements, shapes and characters can be drawn by carefully controlling the application of the electric field. Unlike cathode ray tubes (CRTs), non-emissive flat panel displays are not self-illuminating. Therefore, some sort of backlighting of the flat panel display pixel matrix is typically required in order for the flat panel display to be viewed.
Edge lighting of avionics flat panel displays for dual mode night vision (NVIS) or primary lighting is well known in the art. Traditional applications of the technology have required significant complexity in geometry, space, and cost in order to be effective. Traditional dual mode approaches to lighting avionics flat panel displays have combined fluorescent lamps and light emitting diodes (LEDs), or filtered fluorescent and fluorescent lamps, in order to meet NVIS radiance limits. This conventional approach consumes a substantial amount of packing space and makes flat panel displays anything but flat. The depth required to edge light for NVIS modes of operation adds considerable depth to the flat panel display. Additionally, the circuit card requirements for driving both light sources positioned directly behind the flat panel display pixel matrix (for day mode operations) and light sources positioned behind and to the sides of the flat panel display pixel matrix (for NVIS mode operations) adds considerable cost to the display manufacturing process.
Consequently, an improved dual mode backlight for flat panel displays which overcomes these and other problems would be a significant improvement in the art.
Disclosed are a flat panel display and a backlight which provides both night vision and day mode backlighting of the flat panel display. The backlight of the flat panel display includes a circuit card and day mode light emitting diodes (LEDs) positioned coplanar with each other on the circuit card. Night vision (NVIS) LEDs are positioned on the circuit card coplanar with the day mode LEDs. An optical wave-guide is positioned in front of the day mode LEDs and the NVIS LEDs and is adapted to distribute light from the day mode LEDs and from the NVIS LEDs forward away from the LEDs and the circuit card.